The present invention relates to a sensor device for outputting a detection signal corresponding to a quantity of state of a detection subject, a motor control device using the sensor device, and an electric power steering apparatus using the motor control device.
An electric power steering apparatus, which assists in steering operation by the driver by applying assist torque from a motor to the steering mechanism of a vehicle, is known. The electric power steering apparatus includes a torque sensor for detecting steering torque applied by the driver to the steering mechanism and a motor control device for controlling the driving of a motor. The torque sensor includes a sensor section for detecting changes in the steering torque and outputs a detection signal corresponding to the steering torque detected by the sensor section to the motor control-device. The motor control device obtains a steering torque value based on the detection signal from the torque sensor and sets an assist command value based on the obtained torque value. The motor control device controls the driving of the motor such that the assist torque of the motor follows the assist command value.
However, if an abnormality occurs in the sensor section of the electric power steering apparatus, the electric power steering apparatus cannot detect the steering torque. This hampers control of the driving of the motor by the electric power steering apparatus. To solve this problem, as described in Japanese Laid-open Patent Publication No. 2005-300267, a conventional electric power steering apparatus has a torque sensor configured as a dual system (in accordance with redundant design) including two sensor sections. In this configuration, even if an abnormality occurs in one of the two sensor sections, the motor control device is able to continuously control the driving of the motor using the other sensor section, which operates normally.